This invention relates generally to potentiometers for use in sensing physical movement of an actuator and for converting that physical movement into analog signals that can be translated by a computer into spatial coordinates. More specifically, this invention relates to a potentiometer that can be used in a computer pointing or control device, such as a joystick or mouse, or in a manikin joint.
Traditionally, joysticks use standard one-axis potentiometers to measure relative movement and determine spatial positioning of a joystick actuator from a centering point. Specifically, in a conventional joystick, a first potentiometer, configured along one axis (i.e., an X axis), measures movement and position of the joystick actuator along that axis only. A separate potentiometer is configured along a second axis (i.e., a Y axis) to measure movement and position of the joystick actuator along that axis. A third potentiometer can also be used to measure movement and position along a third axis (i.e., a Z axis). Multiple potentiometers are therefore required to determine the spatial coordinates (X, Y, Z) corresponding to the position of the joystick actuator. Conventional joysticks are generally unable to measure an angle of rotation of the joystick actuator, and when such capability is provided, it requires the use of yet another potentiometer.
A conventional computer mouse, in general, does not contain potentiometers. Optical encoders are instead used to measure an X:Y coordinate position of the mouse. Modem mice use rotating strobe wheels that are optically read. Older mice used a special optical pad with printed lines that were read directly by optical sensors in the mouse. Relatively new force-sensing resistor based mice use miniature X:Y joysticks to determine mouse position. These devices employ a thin film force sensor which changes resistance based on pressure. This joystick responds to force only, and does not move. Except for the force-sensing resistance mouse, a computer mouse is generally unable to determine a relative position of the mouse because it lacks a fixed centering point. In a conventional computer mouse, a ball contacts two strobe wheels contained inside the mouse housing. Each of the strobe wheels is rotatably mounted within the housing and communicates with an optical encoder. Each encoder detects movement along a single axis (i.e., an X or a Y axis). As the mouse moves, friction between the ball and a surface (i.e., a mouse pad or a desk) rotates the ball. Rotation of the ball, in turn, rotates each of the strobe wheels in a direction and amount dependent on the direction and amount of mouse movement. A first encoder detects rotation of the first strobe wheel and generates an electrical signal based on the direction and amount of rotation. A second encoder detects rotation of the second strobe wheel and generates an electrical signal based on the direction and amount of rotation of that strobe wheel. These electrical signals are then sent to a computer for translation into X and Y axis displacement data, proportional to the direction and amount of physical movement of the mouse. This displacement data can then be used to control a screen pointer or to perform other desired computer operations. Conventional computer mice are generally only able to measure movement along an X, Y plane, and are further unable to detect angular movement of the mouse.